Explanation:
Separated by about 14 degrees
(28 Full Moons) in planet Earth's sky,
spiral galaxies M31 at left, and M33 are both large members of
the Local
Group, along with our own Milky Way galaxy.
This narrow- and wide-angle,
multi-camera
composite finds details of spiral structure
in both, while the massive neighbouring galaxies seem to be balanced
in starry fields either side of
bright Mirach, beta star in
the constellation Andromeda.
Mirach is just 200 light-years from the Sun.
But M31, the Andromeda Galaxy,
is really 2.5 million light-years distant and
M33, the Triangulum Galaxy, is also about
3 million light years away.
Although they look far apart,
M31 and M33 are engaged in a gravitational struggle.
In fact, radio astronomers have
found indications of
a bridge of neutral hydrogen gas that could connect the two,
evidence of a closer encounter in the past.
Based on measurements, gravitational
simulations currently
predict that the Milky Way, M31, and M33
will all undergo mutual close encounters and potentially
mergers, billions of years
in the future.